All calls from 213-973-64XX are SPAM.

Called me a few minutes ago, my caller ID said "stupid caller." I didn't pick up, but they didn't leave a message.

I don't know who it was but it apparently was blocked.

Called me twice and did not leave a message.

This number makes repeated nuisance calls to my unlisted cell phone, on which I don't accept calls.  Not even my friends have this number.

If anyone makes a positive ID on this number, Please post it so I can pursue them.  Thanks!

Another complaint site lists the following information about it:
Phone number: 213-973-6430 is located in Los Angeles, California.

Its exchange 973 is managed by COMCAST PHONE OF CALIFORNIA, L.
The number is currently on switch number LSANCA024KD.
Around 66% of people reported it as "Unknown".